PPRuNe Forums - nose wheel investigation

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underfire

13th Sep 2018 13:34

nose wheel investigation

Failure of nose landing gear axle, on departure from London Stansted, 15 September 2017.

https://www.gov.uk/aaib-reports/aaib...737-800-ei-dlv

https://cimg2.ibsrv.net/gimg/pprune....7311a7ed18.jpg

DaveReidUK

13th Sep 2018 17:02

Nose wheel investigation

Or, to be precise, a "no wheel" investigation. :O

PAXboy

13th Sep 2018 17:44

That wheelie good picture shows the strength of the NLG, seriously impressive and reassuring.

Prober

13th Sep 2018 17:56

No(se) Wheel

Many years ago, taxying out at AMS, the aircraft ahead of us (73-200 IIRC) lost a nosewheel turning on to line up for immediate T/O. I called the tower and eventually (after what seemed a very long time) the aircraft came to a stop.

Some months later I received a parcel from the airline concerned, containing a letter of thanks and a DIY model kit of the aircraft. One of my boys built the model and – guess what – the nose wheel fell off!
Prober

DaveReidUK

13th Sep 2018 18:02

Quote:

Originally Posted by PAXboy (Post 10248510)

That wheelie good picture shows the strength of the NLG, seriously impressive and reassuring.

Somewhat unnecessarily, the report takes pains to recount that on landing at EMA, the commander "lowered the nosewheel as gently as possible onto the runway", further reporting that the maximum de-rotation rate for the landing was -1.4°/sec.

That's equivalent to your watch's sweep second hand rotating at about a quarter its normal rate.

HEATHROW DIRECTOR

13th Sep 2018 18:31

Prober - it was obviously meant to happen. When I worked abroad a Comet, operated by a Middle Eastern airline, dropped a wheel as it taxied out, I told the crew and they eventually stopped. Later I heard that a passenger had informed a stewardess and had been told : "It's OK , sir, it's meant to happen"!

pattern_is_full

13th Sep 2018 20:06

Marshaller did a good job of centering that single wheel on the line. ;)

Tom Cundall

14th Sep 2018 07:05

I've noticed more nosewheel tyre changes on the 738 since our company went for single-engine taxi out. Saves 10kg of fuel, costs a fortune in rubber. Anyone know what a tyre costs on a 737?

KelvinD

14th Sep 2018 07:21

A week or so back, I was heading out to Gatwick to get some photos and I checked Planefinder to confirm flights were landing from the West and "watched" a Virgin A330 approaching and then aborting the landing when almost down. The aircraft spent some time in the WILLO hold and, after a detour over Kent, eventually landed. It transpired it was experiencing problems with nose wheel steering (the runway was closed for an hour after landing). I was wondering how did they know there was a problem with the steering prior to landing? Does the pilot give the steering a bit of a wiggle once the gear has been extended?

Cheltman

14th Sep 2018 08:14

The steering system automatically does a short "wiggle" after extension to check all is OK.

Dan_Brown

14th Sep 2018 09:13

Quote:

Originally Posted by Tom Cundall (Post 10248848)

I've noticed more nosewheel tyre changes on the 738 since our company went for single-engine taxi out. Saves 10kg of fuel, costs a fortune in rubber. Anyone know what a tyre costs on a 737?

Exactly. What surprises me it took 8 posts for the obvious to be stated.

Not only rubber but the nose wheel and surrounding structure must take a hammering. Bend metal often enough and long enough, it will crack and break.

What about the increased risk of FOD due to the higher power needed for taxi on the live engine?

Uplinker

14th Sep 2018 10:38

Can I assume that 737s single engine taxi on the No 2 engine? If so, the force from that engine would push the left noeswheel against the base of its axle, which is apparently what caused the “abusive grinding” (great phrase!) of the axle and which led to its eventual failure.

Quote:

That wheelie good picture shows the strength of the NLG, seriously impressive and reassuring

Well, yes and no - half of it broke, the other half took the load ! Unless the aircraft was at max take-off weight and max allowable forward CoG, the nose gear would not have been near its maximum or operating limit. I am sure the nose gear will have been designed to withstand the force from the remaining wheel if the other fails at max allowable weight, so it will be plenty strong enough.

fdr	14th Sep 2018 10:39

Quote:

Originally Posted by Tom Cundall (Post 10248848)

I've noticed more nosewheel tyre changes on the 738 since our company went for single-engine taxi out. Saves 10kg of fuel, costs a fortune in rubber. Anyone know what a tyre costs on a 737?

about 2,500USD each last time I bought some. Then of course, you have to do the NDT for the rim on each change, and if that is outsourced, that runs another 2K USD each rim, more or less. At a 1000USD/Ton for gas, then that is about $10 saving per sector for single engine taxi, on the figures given. If you are paying retail, which is a fair bit more expensive than the airlines would be doing, then the nose wheel changes could be up to 7K a pair including NDT. That would mean you would want to get about 700 landings in between tyre changes to break even.

DaveReidUK

14th Sep 2018 12:31

Quote:

Originally Posted by Uplinker (Post 10248985)

"Abusive grinding" is a reference to a process that occurred during manufacture.

Uplinker

16th Sep 2018 09:05

Quote:

Originally Posted by DaveReidUK (Post 10249084)

"Abusive grinding" is a reference to a process that occurred during manufacture.

Ah yes. Actually during refurbishment, but thanks, I mis-read that.

Capn Bloggs

16th Sep 2018 10:20

Quote:

Marshaller did a good job of centering that single wheel on the line.

Over the wet paint?? :=

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